US Bridges

US 1 Nb/Lowr Deck over Water Mystic River

Fair

Suffolk County, Massachusetts · Big Mys Lower · Structure no. B160174X3DOTNBI

Built
1950
75 years old
Condition
Fair
inspected November 2023
Type
Truss - Thru
Steel Continuous
Length
1,524 ft
3 main spans
Daily traffic
42,492
2022 count
Owner
State
State Highway Agency

About this bridge

US 1 Nb/Lowr Deck over Water Mystic River is a steel continuous truss - thru carrying US 1 Nb/Lowr Deck over Water Mystic River in Suffolk County, Massachusetts. It was built in 1950, so it is 75 years old, older than the Massachusetts average of 63.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 42,492 vehicles a day, roughly 7% of them trucks, projected to reach 70,595 by 2032. The structure is 1,524 ft (464.5 m) long and 42 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

Open in Google Maps
CarriesUS 1 Nb/Lowr Deck
CrossesWater Mystic River
LocationBig Mys Lower
RouteU.S. Route 1
CountySuffolk County
StateMassachusetts
Coordinates42.3851, -71.04729
Functional classUrban Principal Arterial - Other Freeway or Expressway

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionNovember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating40.1 US tons
Inventory rating24 US tons

Structure

Structure typeTruss - Thru
MaterialSteel Continuous
DeckClosed grating
Main spans3
Design loadHS 20
Structure length1,524 ft (464.5 m)
Longest span801 ft (244.1 m)
Deck width42 ft (12.7 m)
Roadway width36 ft (11 m)
Vertical clearance over deck16 ft (4.9 m)

Traffic and service

Average daily traffic42,492 (2022)
Projected traffic70,595 by 2032
Trucks7%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed5 mi (8 km)
TollToll bridge
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$57.5 million (2025 estimate)
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was US 1 Nb/Lowr Deck over Water Mystic River built?

It was built in 1950, making it 75 years old in 2025.

What condition is US 1 Nb/Lowr Deck over Water Mystic River in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in November 2023.

How much traffic does US 1 Nb/Lowr Deck over Water Mystic River carry?

About 42,492 vehicles per day (2022 count), of which roughly 7% are trucks.

How long is US 1 Nb/Lowr Deck over Water Mystic River?

The structure is 1,524 ft (464.5 m) long with a longest span of 801 ft (244.1 m) and a deck 42 ft wide.

Who owns US 1 Nb/Lowr Deck over Water Mystic River?

It is owned by the State Highway Agency.